The Usefulness of Reconstructed 3D Images in Surgical Planning for Cochlear Implantation in a Malformed Ear with an Abnormal Course of the Facial Nerve

Hara, Minoru; Takahashi, Haruo; Kanda, Yukihiko

Abstract

OBJECTIVES
It is not unusual for a cochlear implantation (CI) candidate to have some type of ear malformation, in particular an abnormal course of the facial nerve (FN). In this study, we attempted to reconstruct a three-dimensional (3D) image of temporal bone structures with malformation using computed tomography (CT) imaging and examined its usefulness in the surgical planning of CI in a malformed ear.
METHODS
We prepared 3D images for 6 separate CI cases before surgery. First, we manually colored preoperative CT images using Photoshop CS Extended. We then converted the colored CT images to 3D images using Delta Viewer, free-ware for Macintosh. Before surgery, we discussed any problems anticipated based on the 3D images and plans for surgery with those who would be performing the CI.
RESULTS
Case 1: The subject was a 3-year-old boy with malformed ossicles, semicircular canal (SC) hypoplasia, internal auditory canal stenosis, and an abnormal course of the FN. 3D image indicated that the stapes were absent, and the FN was more anteriorly displaced, so that it was difficult to perform cochleostomy. The surgical findings were similar to those depicted on the 3D image, so we could insert an electrode based on the preoperative image simulation without complications. Case 2: The subject was a 7-year-old boy with malformed stapes, atresia of the round window, cochlear and SC aplasia, and an abnormal course of the FN with bifurcation. CI was performed with no problems, in the same manner as in Case 1.
CONCLUSION
We were able to successfully depict the structures of the inner ear, ossicles, and FN as 3D images, which are very easy to understand visually and intuitively. These 3D images of the malformed ear are useful in preoperative image simulation and in surgical planning for those performing a CI procedure.